Locking mechanisms for fixation devices and methods of engaging tissue

ABSTRACT

Devices, systems and methods are provided for tissue approximation and repair at treatment sites. In particular, fixation devices are provided comprising a pair of elements each having a first end, a free end opposite the first end, and an engagement surface therebetween for engaging the tissue, the first ends being moveable between an open position wherein the free ends are spaced apart and a closed position wherein the free ends are closer together with the engagement surfaces generally facing each other. The fixation devices also include a locking mechanism coupled to the elements for locking the elements in place. The devices, systems and methods of the invention will find use in a variety of therapeutic procedures, including endovascular, minimally-invasive, and open surgical procedures, and can be used in various anatomical regions, including the abdomen, thorax, cardiovascular system, heart, intestinal tract, stomach, urinary tract, bladder, lung, and other organs, vessels, and tissues. The invention is particularly useful in those procedures requiring minimally-invasive or endovascular access to remote tissue locations, where the instruments utilized must negotiate long, narrow, and tortuous pathways to the treatment site.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims the benefit and priority of U.S. ProvisionalPatent Application No. 60/571,217, filed May 14, 2004, and is acontinuation-in-part of U.S. patent application Ser. No. 10/441,531,filed May 19, 2003 which is a continuation-in-part of, and claims thebenefit of priority from U.S. Pat. No. 6,752,813, filed Jun. 27, 2001,which is a continuation-in-part of U.S. Pat. No. 6,629,534, filed Apr.7, 2000, which claims the benefit of prior Provisional Application No.60/128,690, filed on Apr. 9, 1999 under 37 CFR §1.78(a), the fulldisclosures of which are hereby incorporated herein by reference.

In addition, U.S. patent application Ser. No. 10/441,531 is related toU.S. patent application Ser. No. 10/441,753, U.S. patent applicationSer. No. 10/441,508, and U.S. patent application Ser. No. 10/441,687,all of which were filed on the same day (May 19, 2003), the fulldisclosures of which are incorporated herein by reference.

STATEMENT AS TO RIGHTS TO INVENTIONS MADE UNDER FEDERALLY SPONSOREDRESEARCH AND DEVELOPMENT

Not Applicable

REFERENCE TO A “SEQUENCE LISTING,” A TABLE, OR A COMPUTER PROGRAMLISTING APPENDIX SUBMITTED ON A COMPACT DISK.

Not Applicable

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates generally to medical methods, devices, andsystems. In particular, the present invention relates to methods,devices, and systems for the endovascular, percutaneous or minimallyinvasive surgical treatment of bodily tissues, such as tissueapproximation or valve repair. More particularly, the present inventionrelates to repair of valves of the heart and venous valves.

Surgical repair of bodily tissues often involves tissue approximationand fastening of such tissues in the approximated arrangement. Whenrepairing valves, tissue approximation includes coapting the leaflets ofthe valves in a therapeutic arrangement which may then be maintained byfastening or fixing the leaflets. Such coaptation can be used to treatregurgitation which most commonly occurs in the mitral valve.

Mitral valve regurgitation is characterized by retrograde flow from theleft ventricle of a heart through an incompetent mitral valve into theleft atrium. During a normal cycle of heart contraction (systole), themitral valve acts as a check valve to prevent flow of oxygenated bloodback into the left atrium. In this way, the oxygenated blood is pumpedinto the aorta through the aortic valve. Regurgitation of the valve cansignificantly decrease the pumping efficiency of the heart, placing thepatient at risk of severe, progressive heart failure.

Mitral valve regurgitation can result from a number of differentmechanical defects in the mitral valve or the left ventricular wall. Thevalve leaflets, the valve chordae which connect the leaflets to thepapillary muscles, the papillary muscles or the left ventricular wallmay be damaged or otherwise dysfunctional. Commonly, the valve annulusmay be damaged, dilated, or weakened limiting the ability of the mitralvalve to close adequately against the high pressures of the leftventricle.

The most common treatments for mitral valve regurgitation rely on valvereplacement or repair including leaflet and annulus remodeling, thelatter generally referred to as valve annuloplasty. A recent techniquefor mitral valve repair which relies on suturing adjacent segments ofthe opposed valve leaflets together is referred to as the “bow-tie” or“edge-to-edge” technique. While all these techniques can be veryeffective, they usually rely on open heart surgery where the patient'schest is opened, typically via a sternotomy, and the patient placed oncardiopulmonary bypass. The need to both open the chest and place thepatient on bypass is traumatic and has associated high mortality andmorbidity.

For these reasons, it would be desirable to provide alternative andadditional methods, devices, and systems for performing the repair ofmitral and other cardiac valves. Such methods, devices, and systemsshould preferably not require open chest access and be capable of beingperformed either endovascularly, i.e., using devices which are advancedto the heart from a point in the patient's vasculature remote from theheart or by a minimally invasive approach. Further, such devices andsystems should provide features which allow repositioning and optionalremoval of a fixation device prior to fixation to ensure optimalplacement. Still further, the fixation devices should be able to belocked in a fixed position and left behind for implantation. Still morepreferably, the methods, devices, and systems would be useful for repairof tissues in the body other than heart valves. At least some of theseobjectives will be met by the inventions described hereinbelow.

DESCRIPTION OF THE BACKGROUND ART

Minimally invasive and percutaneous techniques for coapting andmodifying mitral valve leaflets to treat mitral valve regurgitation aredescribed in PCT Publication Nos. WO 98/35638; WO 99/00059; WO 99/01377;and WO 00/03759.

Maisano et al. (1998) Eur. J. Cardiothorac. Surg. 13:240-246; Fucci etal. (1995) Eur. J. Cardiothorac. Surg. 9:621-627; and Umana et al.(1998) Ann. Thorac. Surg. 66:1640-1646, describe open surgicalprocedures for performing “edge-to-edge” or “bow-tie” mitral valverepair where edges of the opposed valve leaflets are sutured together tolessen regurgitation. Dec and Fuster (1994) N. Engl. J. Med.331:1564-1575 and Alvarez et al. (1996) J. Thorac. Cardiovasc. Surg.112:238-247 are review articles discussing the nature of and treatmentsfor dilated cardiomyopathy.

Mitral valve annuloplasty is described in the following publications.Bach and Bolling (1996) Am. J. Cardiol. 78:966-969; Kameda et al. (1996)Ann. Thorac. Surg. 61:1829-1832; Bach and Bolling (1995) Am. Heart J.129:1165-1170; and Bolling et al. (1995) 109:676-683. Linear segmentalannuloplasty for mitral valve repair is described in Ricchi et al.(1997) Ann. Thorac. Surg. 63:1805-1806. Tricuspid valve annuloplasty isdescribed in McCarthy and Cosgrove (1997) Ann. Thorac. Surg. 64:267-268;Tager et al. (1998) Am. J. Cardiol. 81:1013-1016; and Abe et al. (1989)Ann. Thorac. Surg. 48:670-676.

Percutaneous transluminal cardiac repair procedures are described inPark et al. (1978) Circulation 58:600-608; Uchida et al. (1991) Am.Heart J. 121: 1221-1224; and Ali Khan et al. (1991) Cathet. Cardiovasc.Diagn. 23:257-262.

Endovascular cardiac valve replacement is described in U.S. Pat. Nos.5,840,081; 5,411,552; 5,554,185; 5,332,402; 4,994,077; and 4,056,854.See also U.S. Pat. No. 3,671,979 which describes a catheter fortemporary placement of an artificial heart valve.

Other percutaneous and endovascular cardiac repair procedures aredescribed in U.S. Pat. Nos. 4,917,089; 4,484,579; and 3,874,338; and PCTPublication No. WO 91/01689.

Thoracoscopic and other minimally invasive heart valve repair andreplacement procedures are described in U.S. Pat. Nos. 5,855,614;5,829,447; 5,823,956; 5,797,960; 5,769,812; and 5,718,725.

BRIEF SUMMARY OF THE INVENTION

The invention provides devices, systems and methods for tissueapproximation and repair at treatment sites. The devices, systems andmethods of the invention will find use in a variety of therapeuticprocedures, including endovascular, minimally-invasive, and opensurgical procedures, and can be used in various anatomical regions,including the abdomen, thorax, cardiovascular system, heart, intestinaltract, stomach, urinary tract, bladder, lung, and other organs, vessels,and tissues. The invention is particularly useful in those proceduresrequiring minimally-invasive or endovascular access to remote tissuelocations, where the instruments utilized must negotiate long, narrow,and tortuous pathways to the treatment site. In addition, many of thedevices and systems of the invention are adapted to be repositionable orreversible and removable from the patient at any point withoutinterference with or trauma to internal tissues.

In preferred embodiments, the devices, systems and methods of theinvention are adapted for fixation of tissue at a treatment site.Exemplary tissue fixation applications include cardiac valve repair,septal defect repair, patent foramen ovale repair, vascular ligation andclamping, laceration repair and wound closure, but the invention mayfind use in a wide variety of tissue approximation and repairprocedures. In a particularly preferred embodiment, the devices, systemsand methods of the invention are adapted for repair of cardiac valves,and particularly the mitral valve, as a therapy for regurgitation. Theinvention enables two or more valve leaflets to be coapted using an“edge-to-edge” or “bow-tie” technique to reduce regurgitation, yet doesnot require open surgery through the chest and heart wall as inconventional approaches.

Using the devices, systems and methods of the invention, the mitralvalve can be accessed from a remote surgical or vascular access pointand the two valve leaflets may be coapted and fixed together usingendovascular or minimally invasive approaches. The devices of thepresent invention include a fixation device having a locking mechanismwhich allows the user to “lock” the fixation devices in a desiredposition to fix the leaflets together. In some embodiments, the lockingmechanism locks the fixation device in a single predeterminedconfiguration or in one of a few predetermined configurations. In otherembodiments, the locking mechanism allows locking at any point along acontinuum of points on the device so that the user may choose thedesired position for fixing the leaflets together during the procedure.The desired position for fixing the leaflets may vary due to variabilityin the thickness and amount of tissue captured by the fixation device,the presence or absence of disease (e.g. calcification, hypertrophy),the age of the patient and other factors potentially unknown to the userprior to the procedure. For example, if more tissue is captured orcoapted by the fixation device, the fixation device may not be able toclose as far than if less tissue is captured. Therefore, in somecircumstances it may be advantageous that the locking mechanism of thefixation device be lockable at a specific, non-predetermined pointdesired by the user even though that point may not be able to bedetermined prior to the procedure.

In some circumstances the invention may also find application in opensurgical approaches as well. According to the invention, the mitralvalve may be approached either from the atrial side (antegrade approach)or the ventricular side (retrograde approach), and either through bloodvessels or through the heart wall.

In a first aspect of the present invention, a fixation device isprovided having a pair of distal elements (or fixation elements), eachdistal element having a free end and an engagement surface for engagingthe tissue, wherein the distal elements are moveable between a firstposition for capturing the tissue and a second position for fixing thetissue. Preferably, the engagement surfaces are spaced apart in thefirst position and are closer together and generally face toward eachother in the second position. The fixation device is preferablydelivered to a target location in a patient's body by a deliverycatheter having an elongated shaft, a proximal end and a distal end, thedelivery catheter being configured to be positioned at the targetlocation from a remote access point such as a vascular puncture orcut-down or a surgical penetration. In a preferred embodiment, thetarget location is a valve in the heart.

In a second aspect of the present invention, the fixation device furtherincludes a locking mechanism that maintains the distal elements in aselected position relative to each other. While a variety of lockingmechanisms may be used. In some embodiments, the fixation deviceincludes a moveable stud coupled to the fixation elements whereinmovement of the stud moves the fixation elements between the positions.In such embodiments, the locking mechanism may comprise an engagementelement engageable with the moveable stud wherein engagement restrictsmovement of the stud. In some instances, the engagement elementcomprises at least one wedging element which frictionally engages themoveable stud to restrict movement of the stud. In other embodiments,the engagement element has at least one protrusion which mates with atleast one external groove on the stud so as to restrict movement of thestud.

Alternatively, the locking mechanism may comprises an interferenceelement which is positionable along the moveable stud so that theinterference element prevents movement of the moveable stud in at leasta first direction by contacting a stationary surface of the fixationdevice. In some embodiments, the interference element comprises alocking sheath advanceable over the moveable stud so that the lockingsheath prevents movement of the stud in the at least first direction byabutting against the stationary surface. In other embodiments, themoveable stud includes external grooves and the interference elementcomprises a lock nut mateable with the external grooves of the moveablestud so that the mated lock nut prevents movement of the stud in atleast the first direction by abutting against the stationary surface.

It may be appreciated that the moveable stud may be comprised of a rigidmaterial, such as a metal or plastic, or the moveable stud may becomprised of a flexible line, such as a suture. When the moveable studcomprises a flexible line, the locking mechanism may comprise aninterference element which is positionable along the flexible line sothat the interference element prevents movement of the flexible line inat least a first direction by contacting a stationary surface of thefixation device.

In still other embodiments, the locking mechanism comprises gears,wherein movement of the gears moves the fixation elements between thepositions while locking the fixation elements in place at each position.

Further, in other embodiments, the locking mechanism comprises a biasingmember which biases the fixation elements toward one of the positions.The biasing member may comprise a pair of spring loaded support sleevespositionable against a portion of the fixation device so as to bias thefixation elements toward one of the positions. Or, the biasing membermay comprise a cinching band positionable around the fixation elementsso as to bias the fixation elements toward one of the positions. In someembodiments, the cinching band comprises an elastic cinching bandpositionable around the fixation elements in a stretched configurationso as to apply biasing force to the fixation elements. In otherembodiments, the cinching band comprises a cinching line positionablearound the fixation elements in a lasso configuration so as to applybiasing force to the fixation elements when tightened.

Typically, the fixation further comprises at least one leg joined withthe fixation elements so that movement of the at least one leg moves thefixation elements between the positions. In such embodiments, the atleast one leg may have a spring loaded configuration so as to bias thefixation elements toward one of the positions. Alternatively or inaddition, the locking mechanism may comprise a structure joinable withthe at least one leg so as to prevent movement of the fixation elements.In some embodiments, the structure comprises a barb engagable with theat least one leg.

In a third aspect of the present invention, the fixation devices includean unlocking mechanism for disengaging the locking mechanism. In someembodiments, the unlocking mechanism comprises a harness, the harnessadapted to disengage or reduce engagement of an engaging element fromthe moveable stud. For example, the harness may reduce frictionalengagement a wedging element against the moveable stud.

In other aspect of the present invention, a locking mechanism coupled tothe fixation elements is provided for locking the fixation elements inplace along a continuum of positions between the open position and theclosed position. Again, the fixation device may include a moveable studcoupled to the fixation elements wherein movement of the stud moves thefixation elements between the positions. In such embodiments, thelocking mechanism may comprise at least one wedging element forfrictionally engaging the stud to restrict movement thereof. Forexample, the at least one wedging element may comprise a binding platehaving a first end, a second end and a portion therebetween shaped toengage the stud, the binding plate positioned so that the portion isdisposed near the stud. The portion shaped to engage the stud may atleast partially surround the stud and the binding plate may bepositioned so that the portion at least partially surrounds the stud. Insome embodiments, the portion shaped to at least partially surround thestud comprises an aperture, wherein the binding plate is positioned sothat the stud passes through the aperture. The locking mechanism mayfurther comprise a spring which forces the aperture against the stud torestrict movement of the stud through the aperture.

In some embodiments, the at least one wedging element comprises at leastone cam, the at least one cam pivotable to frictionally engage the studto restrict movement thereof. The at least one cam may have an inwardsurface engageable with the stud and an outward surface connected with aspring which forces the inward surface against the stud to restrictmovement of the stud. Embodiments including an unlocking mechanism fordisengaging the locking mechanism, may include at least one actuatorattached to a pivot point on each of the at least one cams, the at leastone actuator adapted to pivot the at least one cam about its pivot pointto reduce frictional engagement of the inner surface with the stud.Sometimes, the at least one cam comprises two cams, each cam disposed onopposite sides of the stud.

In another aspect of the present invention, a locking mechanism coupledto the fixation elements is provided for locking the fixation elementsin a position which allows movement of the fixation elements within asub-range of the range. For example, in embodiments having a moveablestud coupled to the fixation elements wherein movement of the stud movesthe fixation elements between the positions within the range, the studmay have may have at least one external groove for engagement by atleast one wedging element wherein the at least one external groove issized to allow shifting of the at least one wedging element within theat least one external groove which allows movement of the fixationelements within the sub-range. In other embodiments having such amoveable stud, the locking mechanism comprises at least one wedgingelement for frictionally engaging the stud to restrict movement thereof.In some instances, the at least one wedging element comprises an atleast partially flexible material wherein flexing of the material allowsmovement of the fixation elements within the sub-range. In otherinstances, the at least one wedging element comprises a binding platehaving a first end, a second end and a portion therebetween shaped to atleast partially surround the stud, the binding plate positioned so thatthe portion at least partially surrounds the stud. In some embodiments,the portion shaped to at least partially surround the stud comprises anaperture and the binding plate is positioned so that the stud passesthrough the aperture.

It may be appreciated that the fixation elements may be configured forengaging valve leaflets of a valve within a heart, and movement of thefixation elements within the sub-range is achievable by force caused bydynamic fluid flow through the valve.

In another aspect of the present invention, a locking mechanism isprovided comprising a moveable stud coupled to a device, whereinmovement of the stud actuates movement of a portion of a device to adesired position in a range from a first position to a second position,at least one element configured to engage the stud to restrict movementof the stud which locks the device in the desired position, and anunlocking mechanism configured to disengage the at least one elementfrom the stud which allows movement of the stud. In some instances, theat least one element comprises a binding plate having a first end, asecond end and a portion therebetween shaped to at least partiallysurround the stud, the binding plate positioned so that the portion atleast partially surrounds the stud. The portion shaped to at leastpartially surround the stud may comprise an aperture, the binding platepositioned so that the stud passes through the aperture. In someembodiments, the locking mechanism further comprising a springconfigured to force the aperture against the stud to restrict movementof the stud through the aperture. The unlocking mechanism may comprise aharness, the harness adapted to move the second end while the first endremains substantially stationary so as to reduce frictional engagementof the at least partially surrounding portion with the stud.

In some embodiments, the at least one element comprises at least onecam, the at least one cam pivotable to frictionally engage the stud torestrict movement thereof. The at least one cam may have an inwardsurface engageable with the stud and an outward surface connected with aspring which forces the inward surface against the stud to restrictmovement of the stud. In some embodiments, the unlocking mechanismcomprises at least one actuator attached to a pivot point on each of theat least one cams, the at least one actuator adapted to pivot the atleast one cam about its pivot point to reduce frictional engagement ofthe inner surface with the stud.

In still other embodiments, the moveable stud may have at least oneexternal groove for engagement with the at least one element to restrictmovement of the stud. Thus, the at least one element may comprise atleast one component having at least one protrusion which mates with theat least one external groove of the stud wherein the at least onecomponent is moveable to engage the at least one protrusion with the atleast one external groove of the stud to restrict movement of the stud.In many of these embodiments, the unlocking mechanism comprises a hingecomponent which moves the at least one component to disengage the atleast one protrusion from the at least one external groove. It may beappreciated that the at least one external groove may comprise threadsand the at least one component comprise a split nut.

The desired position typically includes any position between the firstposition and the second position. Likewise, the desired position mayincludes one of a series of predetermined positions between the firstposition and the second position.

In another aspect of the present invention, a lockable system isprovided comprising a device having a portion which is moveable to adesired position, and a locking mechanism coupled to the device. Thelocking mechanism comprises a moveable stud configured so that movementof the stud actuates movement of the portion of the device to thedesired position, at least one element configured to engage the stud torestrict movement of the stud which locks the device in the desiredposition, and an unlocking mechanism configured to disengage the atleast one element from the stud which allows movement of the stud.

In some embodiments, the device comprises a catheter. The catheter mayinclude at least one pullwire fixedly attached to the stud so thatmovement of the stud moves the at least one pullwire which actuatesmovement of the portion of the catheter to the desired position. Inother embodiments, the device comprises a grasper. The grasper mayinclude at least one pullwire fixedly attached to the stud so thatmovement of the stud moves the at least one pullwire which actuatesmovement of the portion of the grasper to the desired position. And, instill other embodiments, the device comprises a retractor.

As mentioned, the locking mechanism of the present invention may beemployed in catheter shafts, retractors, or other medical instrumentssuch as graspers or biopsy forceps, where it is desirable to lock adevice in a particular position prior to, during, or following a medicalprocedure. Such procedures can include biopsies or ablation procedures,wherein it is desired to navigate and hold catheter position, andretrieval procedures (e.g. of polyps, foreign objects).

Other objects and advantages of the present invention will becomeapparent from the detailed description to follow, together with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an embodiment of a fixation device having anembodiment of a locking mechanism.

FIG. 2 illustrates another embodiment of a fixation device having anembodiment of a locking mechanism.

FIG. 3 provides a front view of the locking mechanism of FIG. 1.

FIGS. 4A-4C illustrate the locking mechanism of FIG. 3 in unlocked andlocked positions.

FIGS. 5-7 illustrate elements of an embodiment of a locking mechanismwhich includes a binding plate.

FIGS. 8A-8B illustrate an embodiment of a locking mechanism having aone-sided release harness.

FIGS. 9A-9C illustrate an embodiment of a locking mechanism havingwedging elements comprising binding structures.

FIGS. 10A-10C illustrate an embodiment of a locking mechanism havingwedging elements comprising interdigitating structures.

FIGS. 11A-11B illustrate an embodiment of a locking mechanism comprisinga pair of cams.

FIGS. 12A-12D illustrate elements of an embodiment of a lockingmechanism which includes mateable components having at least oneprotrusion and groove which engage for locking.

FIGS. 13A-13C illustrate an embodiment of a locking mechanism comprisinggears.

FIGS. 14A-14D, 15A-15B illustrate an embodiment of a locking mechanismwhich works against biasing forces that advance the stud of the fixationdevice.

FIGS. 16A-16B illustrate a fixation device having a flexible linereplacing the stud, and wherein the locking mechanism works againstbiasing forces that advance the flexible line.

FIG. 17A illustrates an embodiment of a fixation device having legsspring biased toward a closed position.

FIGS. 17B-17C illustrate the application of support sleeves to bias thedistal elements of the fixation device toward a closed position.

FIGS. 18A-18C illustrate an embodiment of a biasing member comprising acinching band.

FIGS. 19A-19C illustrate an embodiment of a biasing member comprising acinching line.

FIG. 20 illustrates a locking mechanism comprising barbs which attach tothe legs, holding the legs in a fixed position.

FIGS. 21A-21C illustrate attachment of the barbs to the legs.

FIG. 22 illustrates a catheter having an embodiment of a lockingmechanism of the present invention.

FIG. 23 illustrates a grasper having an embodiment of a lockingmechanism of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The fixation devices of the present invention provide for grasping,approximating and fixating tissues such as valve leaflets to treatcardiac valve regurgitation, particularly mitral valve regurgitation. Inpreferred embodiments, the fixation devices provide features that allowrepositioning and removal of the device if so desired. Such removalwould allow the practitioner to reapproach the valve in a new manner ifso desired. Once the tissue has been satisfactorily approximated, thegrasped tissue is typically fixed in place by maintaining grasping withthe fixation device which is left behind as an implant.

The fixation device is releasably attached to a shaft of aninterventional tool at its distal end. When describing the devices ofthe invention herein, “proximal” shall mean the direction toward the endof the device to be manipulated by the user outside the patient's body,and “distal” shall mean the direction toward the working end of thedevice that is positioned at the treatment site and away from the user.With respect to the mitral valve, proximal shall refer to the atrial orupstream side of the valve leaflets and distal shall refer to theventricular or downstream side of the valve leaflets.

Referring to FIG. 1, a fixation device 14 typically comprises proximalelements 16 (or gripping elements) and distal elements 18 (or fixationelements) which protrude radially outward and are positionable onopposite sides of tissue, such as leaflets, so as to capture or retainthe leaflets therebetween at a single location or along a continuum orrange of positions as desired by the user. The fixation device 14 iscoupleable to the shaft of the interventional tool (not shown) by acoupling mechanism, a portion of which is shown as coupling member 19.The coupling mechanism allows the fixation device 14 to detach and beleft behind as an implant to hold the leaflets together in the coaptedposition. The coupling member 19 is either formed with or connected tohousing 3 which typically houses locking mechanism 106.

It may be appreciated that the fixation device 14 may have a variety offorms, of which FIG. 1 is an example. FIG. 2 illustrates anotherembodiment of a fixation device 14. Here, the fixation device 14comprises distal elements 18 (or fixation elements) which protruderadially outward and are positionable on opposite sides of tissue, suchas leaflets, so as to capture or retain the leaflets therebetween alonga continuum as desired by the user. Here the distal elements 18 areformed from a continuous piece of material that is flexed to open andclose by movement of the legs 68, however it may alternatively be hingedat the midpoint thereof. Again the fixation device 14 is coupleable tothe shaft of the interventional tool (not shown) by a couplingmechanism, a portion of which is shown as coupling member 19. Thecoupling mechanism allows the fixation device 14 to detach and be leftbehind as an implant to hold the leaflets together in the coaptedposition.

In these embodiments, the fixation device 14 includes a lockingmechanism for locking the device 14 in a particular position, such as anopen, closed or inverted position or any position therebetween. It maybe appreciated that the locking mechanism includes an unlockingmechanism which allows the device to be both locked and unlocked. FIGS.1-3, 4A-4C illustrate an embodiment of a locking mechanism 106.Referring to FIG. 1, in this embodiment, the locking mechanism 106 isdisposed between the coupling member 19 and the base 69 of the actuationmechanism 58. The base 69 is connected to the legs 68 of the actuationmechanism 58 which are in turn connected to the distal elements 18.Thus, movement of the legs 68 moves the distal elements 18 through open,closed and inverted positions. The base 69 is also fixedly attached to astud 74 which extends through the locking mechanism 106. The stud 74 isreleasably attached to an actuator rod which passes through the couplingmember 19 and the shaft of the interventional tool. Release of the stud74 from the actuator rod allows the fixation device 14 to be detachedand left behind as an implant.

FIG. 1 also illustrates the proximal elements 16, which in thisembodiment straddle the locking mechanism and join beneath the lockingmechanism 106. The proximal elements 16 are shown supported by proximalelement lines 90. The proximal elements 16 are raised and lowered bymanipulation of the proximal element lines 90.

The proximal element lines 90 may be connected with the proximalelements 16 by threading the lines 90 in a variety of ways as describedand illustrated in U.S. patent Ser. No. 10/441,531, incorporated hereinby reference for all purposes. As described and illustrated, a line loop48 may be present on a proximal element 16 through which a proximalelement line 90 may pass and double back. Such a line loop 48 may beuseful to reduce friction on proximal element line 90 or when theproximal elements 16 are solid or devoid of other loops or openingsthrough which the proximal element lines 90 may attach. Line loops 48may be comprised of any suitable material, may be formed into theproximal element 16 itself or may be formed from a material tied onto orattached to the proximal element 16. For example, the line loop 48 maybe comprised of a suture loop which is tied to the proximal element 16,such as through an opening in the proximal element 16. In embodimentswhich include a covering, such as a fabric, mesh, textured weave, felt,looped or porous structure, as described and illustrated in U.S. patentSer. No. 10/441,531, incorporated herein by reference for all purposes,the proximal element lines 90 may be connected to the proximal elements16 by attachment to the covering itself or by passage of the proximalelement lines 90 through the covering and attaching to the proximalelements 16 in any manner described.

In addition, lock lines 92 are shown in FIG. 1 connected with a releaseharness 108 of the locking mechanism 106. The lock lines 92 are used tolock and unlock the locking mechanism 106 as will be described below.The proximal element lines 90 and lock lines 92 may be comprised of anysuitable material, typically wire, nitinol wire, cable, suture orthread, to name a few. In addition, the proximal element lines 90 and/orlock lines 92 may include a coating, such as Parylene®. Parylene® is avapor deposited pinhole free protective film which is conformal andbiocompatible. It is inert and protects against moisture, chemicals, andelectrical charge.

FIG. 3 provides a front view of the locking mechanism 106 of FIG. 1.However, here the proximal elements 16 are supported by a singleproximal element line 90 which is through both of the proximal elements16. In this arrangement both of the elements are raised and loweredsimultaneously by action of a single proximal element line 90. Whetherthe proximal elements 16 are manipulated individually by separateproximal element lines 90 or jointly by a single proximal element line90, the proximal element lines 90 may extend directly through openingsin the proximal elements and/or through a layer or portion of a coveringon the proximal elements, or through a suture loop above or below acovering.

FIGS. 4A-4C illustrate the locking mechanism 106 showing the lockingmechanism 106 in the unlocked and locked positions respectively.Referring to FIG. 4A, the locking mechanism 106 includes one or moreengagement elements, such as wedging elements or rolling elements. Inthis embodiment, the wedging elements comprise a pair of barbells 110disposed on opposite sides of the stud 74, each barbell having a pair ofgenerally cylindrical caps and a shaft therebetween. The barbells 110and the stud 74 are preferably comprised of cobalt chromium or stainlesssteel, however any suitable material may be used.

In some embodiments, each barbell 10 has a higher hardness than the stud74. This hardness difference can enhance the grip or friction of thesurfaces by allowing one element to “dig into” or invaginate into theother surface, even if only slightly. In addition, to improve engagementof the barbells 110 with the stud 74, the stud 74 may include one ormore surface treatments and/or the stud 74 may have a particularcomposition and/or geometry, such as roughened surfaces, raisedprotrusions formed on the surface, frictional elements embedded in thesurface, etc., to enhance surface friction and thereby increase theengagement strength.

The barbells 110 are manipulated by hooked ends 112 of the releaseharness 108. A perspective view of an embodiment of the release harness108 is illustrated in FIG. 4B. When an upwards force is applied to theharness 108 by the lock line 92 (illustrated in FIG. 1), the hooked ends112 raise the barbells 110 against a spring 114, as shown in FIG. 4A.This draws the barbells 110 up along a sidewall or sloping surface 116which unwedges the barbells 110 from against the stud 74. In thisposition, the stud 74 is free to move. Thus, when the lock line 92raises or lifts the harness 108, the locking mechanism 106 is in anunlocked position wherein the stud 74 is free to move the actuationmechanism 58 and therefore the distal elements 18 to any desiredposition. Release of the harness 108 by the lock line 92 transitions thelocking mechanism 106 to a locked position, illustrated in FIG. 4C. Byreleasing the upwards force on the barbells 110 by the hooked ends 112,the spring 114 forces the barbells 110 downwards and wedges the barbells110 between the sloping surface 116 and the stud 74. This restrictsmotion of the stud 74, which in turn locks the actuation mechanism 58and therefore distal elements 18 in place.

In addition, the stud 74 may include one or more grooves 82 orindentations which receive the barbells 110. This may provide more rapidand positive locking by causing the barbells 110 to settle in a definiteposition, increase the stability of the locking feature by furtherpreventing movement of the barbells 110, as well as tangible indicationto the user that the barbell has reached a locking position. Inaddition, the grooves 82 may be used to indicate the relative positionof the distal elements 18, particularly the distance between the distalelements 18. For example, each groove 82 may be positioned to correspondwith a 0.5 or 1.0 mm decrease in distance between the distal elements18. As the stud 74 is moved, the barbells 110 will contact the grooves82; by counting the number of grooves 82 that are felt as the stud 74 ismoved, the user can determine the distance between the distal elements18 and can provide the desired degree of coaptation based upon leafletthickness, geometry, spacing, blood flow dynamics and other factors.Thus, the grooves 82 may provide tactile feedback to the user, and mayalso be visible on fluoroscopy or an echocardiogram to provide visualfeedback. Further, the grooves 82 may be sized to allow shifting ormovement of each barbells 110 within each groove 82. Such shiftingallows the stud 74 to move slightly in the proximal and distaldirection, therefore allowing slight movement of the distal elements 18when the locking mechanism is in the locked position. This may allow thefixation device 14 to open slightly in response to dynamic cardiacforces.

As mentioned, the locking mechanism 106 allows the fixation device 14 toremain in an unlocked position when attached to the interventional tool10 during grasping and repositioning and then maintain a locked positionwhen left behind as an implant. It may be appreciated, however, that thelocking mechanism 106 may be repeatedly locked and unlocked throughoutthe placement of the fixation device 14 if desired. Further, the lockingmechanism 106 depicted in FIGS. 1-3, 4A-4C allows the fixation device 14to be incrementally moved toward the closed position while locked. Asmentioned, movement toward the closed position is achieved by retractingor pulling the stud 74 in the proximal direction so that the distalelements 18 approach each other. Retraction of the stud 74 draws thebarbells 110 upward. Since the sloping surfaces 116 widen in theproximal direction, the barbells 110 are allowed to unwedge in thisdirection. In contrast, extension or pushing of the stud 74 in thedistal direction is resisted by further wedging of the barbells 110between the sloping surfaces 116 and the stud. Once the final placementis determined, the lock line 92 and proximal element lines 90 areremoved and the fixation device is left behind.

FIG. 5 illustrates another embodiment of a locking mechanism 106. Inthis embodiment, the locking mechanism 106 also includes an engagementelement comprising a wedging element. Here the wedging element comprisesa binding lever or binding plate 450. In this embodiment, as shown inFIG. 6, the binding plate 450 has an oblong shape extending between afirst end 452 and a second end 454 with a bottom planar surface 456 anda top planar surface 458. An aperture 460 is formed between the firstand second ends 452, 454 extending from the top planar surface 458through to the bottom planar surface 456. Referring back to FIG. 5, thebinding plate 450 is positioned within the locking mechanism 106 so thatthe stud 74 passes through the aperture 460. FIG. 7 provides a closerview of the binding plate 450 within the locking mechanism 106. Asshown, the first end 452 is positioned within a notch 462 which preventsaxial movement of the first end 452. However, the second end 454 is freeto move in an axial direction thus creating a lever type movement of thebinding plate 450. Movement of the second end 454 is controlled by theassociated hooked end 112 of the release harness 108. When an upwardsforce is applied to the harness 108 by the lock line 92, the hooked end112 raises the second end 454 of the plate 450 against a spring 114 sothat the planar surfaces 456, 458 are substantially perpendicular to thestud 74. This aligns the aperture 460 with the stud 74 allowing freemovement of the stud 74. Thus, in this state, the locking mechanism 106is unlocked wherein the stud 74 is free to move the actuation mechanism58 and therefore the distal elements 18 to any desired position.

Release of the harness 108 by the lock line 92 transitions the lockingmechanism 106 to a locked position. By releasing the upwards force onthe second end 452 of the binding plate 450, the spring 114 forces thesecond end 452 downwards and wedges the aperture 460 against the stud74, as illustrated in FIG. 5 and FIG. 7. This restricts motion of thestud 74, which in turn locks the actuation mechanism 58 and thereforedistal elements 18 in place. It may be appreciated that the bindingplate 450 may have any suitable form to function as described above. Forexample, the plate 450 may have a variety of shapes with or withoutplanar surfaces 456, 458 and/or the aperture 460 may be of a variety ofshapes and positioned in a variety of locations, to name a few. Further,it may be appreciated that any number of binding plates 450 may bepresent. Each binding plate 450 provides an additional binding locationwhich may enhance lock performance.

It may be appreciated that although the above described embodiment ofthe binding plate 450 includes an aperture 460 for passing of the stud74 therethrough, the binding plate 450 may be shaped so as to notinclude such an aperture 460. In such embodiments, the binding plate 450may be shaped to at least partially surround the stud 74, such as havinga notch, inlet or hook-shape through which the stud 74 passes. Thus, thebinding plate 450 would function in the same manner as above wherein theportion at least partially surrounding the stud 74 would engage the stud74 for locking and disengage the stud 74 for unlocking.

The binding plate 450 and the stud 74 may be comprised any suitablematerial. In some embodiments, the binding plate 450 has a higherhardness than the stud 74. In other embodiments, the binding plate 450is comprised of a flexible or semi-flexible material. Such flexibilityallows slight movement of the stud 74 in the proximal and distaldirections, therefore allowing slight movement of the distal elements 18when the locking mechanism is in the locked position. This may allow thefixation device 14 to adjust in response to dynamic cardiac forces.

To improve engagement of the binding plate 450 with the stud 74, thestud 74 may include one or more surface treatments and/or the stud 74may have a particular composition and/or geometry as set forth above.

In this embodiment the stud 74 may include one or more grooves 82 orindentations which receive the binding plate 450, similar to the groovesof the locking mechanism of FIGS. 1-3, 4A-4C. Again, this may providemore rapid and positive locking by causing the binding plate 450 tosettle in a definite position, increase the stability of the lockingfeature by further preventing movement of the binding plate 450, as wellas tangible indication to the user that the binding plate 450 hasreached a locking position. In addition, the grooves 82 may be used toindicate the relative position of the distal elements 18, particularlythe distance between the distal elements 18.

The locking mechanism 106 depicted in FIG. 5 allows the fixation device14 to be incrementally moved toward the closed position while locked.Movement toward the closed position is achieved by retracting or pullingthe stud 74 in the proximal direction so that the distal elements 18approach each other. Retraction of the stud 74 draws the binding plate450 towards a horizontal position, aligning the aperture with the stud74 and thus allowing movement. In contrast, extension or pushing of thestud 74 in the distal direction is resisted by further wedging of thebinding plate 450 against the stud 74. Once the final placement isdetermined, the lock line 92 and proximal element lines 90 are removedand the fixation device is left behind.

FIGS. 8A-8B illustrate a similar embodiment of a locking mechanism.Again, the wedging element comprises a binding plate 450 positionedwithin the housing 3 so that the stud 74 passes through the aperture460. FIG. 8B provides a closer view of the binding plate 450 within thehousing 3. As shown, the first end 452 of the lever 450 is positionedwithin a notch 462 which prevents axial movement of the first end 452.However, the second end 454 of the binding plate 450 is free to move inan axial direction thus creating a lever type movement of the bindingplate 450. Movement of the second end 454 is controlled by theassociated hooked end 112 of the release harness 108. Here, the releaseharness 108 is “one-sided” in comparison to the release harness of FIG.5, i.e. only one hooked end 112 is present. When an upwards force isapplied to the harness 108 by the lock line 92, the hooked end 112raises the second end 454 of the plate 450 against a spring 114 so thatplate 450 is substantially perpendicular to the stud 74. This aligns theaperture 460 with the stud 74 allowing free movement of the stud 74.Thus, in this state, the locking mechanism 106 is unlocked wherein thestud 74 is free to move the actuation mechanism 58 and therefore thedistal elements 18 to any desired position. The “one-sided” harnessimproves ease of use and unlocking consistency throughout variousfixation device positions.

Release of the harness 108 by the lock line 92 transitions the lockingmechanism 106 to a locked position. By releasing the upwards force onthe second end 452 of the binding plate 450, the spring 114 forces thesecond end 452 downwards and wedges the aperture 460 against the stud74. This restricts motion of the stud 74, which in turn locks theactuation mechanism 58 and therefore distal elements 18 in place.

FIGS. 9A-9C illustrate another embodiment of a locking mechanism 106.Referring to FIG. 9A, in this embodiment, the locking mechanism 106 isagain disposed between the coupling member 19 and the base 69 of theactuation mechanism 58. The base 69 is connected to the stud 74 whichextends through the locking mechanism 106, and connects to an actuatorrod which extends through the coupling member 19 and the shaft 12 of theinterventional tool 10. The base 69 is also connected to the legs 68 ofthe actuation mechanism 58 which are in turn connected to the distalelements 18. FIG. 9A also illustrates proximal elements 16 whichmanipulate the locking mechanism 106 in this embodiment. The lockingmechanism 106 includes wedging elements comprising folded leaf orbinding structures 124 having overlapping portions 124a, 124b. Eachfolded binding structure 124 is attached to or continuously formed witha proximal element 16, as shown. In FIG. 9A and FIG. 9B, the foldedstructures 124 are shown without the remainder of the locking mechanism106 (housing) for clarity. The proximal elements 16 are flexible,resilient and biased outwardly. The binding structures 124 include holes125 (FIG. 9C) in each overlapping portion 124 a, 124 b so that the stud74 passes through the holes 125 of the portions 124 a, 124 b as shown.The locking mechanism includes slots into which ends 123 of the bindingstructures 124 are fixed. When the proximal elements 16 are in anundeployed position, as in FIG. 9A, the binding structures 124 liesubstantially perpendicular to the stud 74 so that the holes 125 in eachoverlapping portion are vertically aligned. This allows the stud 74 topass freely through the holes and the locking mechanism 106 isconsidered to be in an unlocked position.

Deployment of the proximal elements 16, as shown in FIG. 9B, tilts thebinding structures 124 so as to be disposed in a non-perpendicularorientation relative to the stud 74 and the holes 125 are no longervertically aligned with one another. In this arrangement, the stud 74 isnot free to move due to friction against the holes of the bindingstructure 124. FIG. 9C provides a larger perspective view of the foldedstructures 124 in this position. Thus, the locking mechanism 106 isconsidered to be in a locked position. This arrangement allows thefixation device 14 to maintain an unlocked position during grasping andrepositioning and then maintain a locked position when the proximalelements 16 are deployed and the fixation device 14 is left behind as animplant. This arrangement also allows locking to be achievedautomatically by releasing of the proximal elements 16. Therefore, thereis no need for a separate actuator for the locking mechanism. Such ascombined function of grasping and locking, thereby eliminating the needfor separate actuation elements, may reduce the profile and complexityof the fixation device, simplifying the user interface. It may also beappreciated, that the locking mechanism 106 may be repeatedly locked andunlocked throughout the placement of the fixation device 14 if desired.

FIGS. 10A-10C illustrate a similar embodiment of a locking mechanism106. Referring to FIG. 10A, in this embodiment, the locking mechanism106 is again disposed between the coupling member 19 and the base 69 ofthe actuation mechanism 58. And, the base 69 is connected to the stud 74which extends through the locking mechanism 106 and connects to anactuator rod which extends through the coupling member 19 and the shaftof the interventional tool 10. FIG. 10A illustrates the proximalelements 16 which manipulate the locking mechanism 106 in thisembodiment. The locking mechanism 106 includes wedging elementscomprising interdigitating structures 128, such as in the shape of a “C”as illustrated, each interdigitating structure 128 attached to aproximal element 16. The interdigitating structures 128 hook around thestud 74 so that the stud 74 passes through the “C” of each structure 128as shown in FIGS. 10B-10C. As shown, the structures 128 cross each otherand the “C” of each structure 128 faces each other. A spring 130 biasesthe interdigitating structures into engagement with one another. Whenthe proximal elements are in an undeployed position, as in FIG. 10B, theinterdigitating structures 128 are urged into an orientation moreorthogonal to the axial direction defined by stud 74, thus bringing the“C” of each structure 128 into closer axial alignment. This allows thestud 74 to pass freely through the “C” of each structure 128. Deploymentof the proximal elements 16 outwardly urges the interdigitatingstructures into a more angular, non-orthogonal orientation relative tostud 74 causing the sidewalls of the “C” of each structure 128 to engagestud 74 more forcefully. In this arrangement, the stud 74 is not free tomove due to friction against the interdigitating structures 128.

FIGS. 11A-11B illustrate another embodiment of a locking mechanism 106.In this embodiment, the locking mechanism 106 also includes at least onewedging element. Here each wedging element comprises a cam 480. FIG. 11Aillustrates a pair of cams 480 disposed on opposite sides of the stud74, each cam 480 having an inward surface 482 and an outward surface484. Each cam 480 is connected to a wall of the locking mechanism 106 bya spring 486 or other mechanism which applies force to the outwardsurface 484 of the cam 480. Such force wedges the inward surface 482 ofthe cam 480 against the stud 74, as shown in FIG. 11A, when in thelocked position. Thus, when the cams 480 are wedged against the stud 74the stud 74 is not free to move and therefore the distal elements 18 arelocked in place.

Each cam 480 is coupled with a actuator 488 at a pivot point 490. Byapplying an upwards force on actuator 488, the associated cam is pivotedaround pivot point 490 so that its inward surface 482 is unwedged fromthe stud 74, as illustrated in FIG. 11B. In this position, the stud 74is free to move. Thus, when the cams 480 are pivoted the lockingmechanism 106 is in an unlocked position wherein the stud 74 is free tomove the actuation mechanism 58 and therefore the distal elements 18 toany desired position. It may be appreciated that any number of cams 480may be present and each cam 480 may have any suitable form to functionas described above.

FIGS. 12A-12D illustrate another embodiment of a locking mechanism 106having at least one engagement element. In this embodiment, the at leastone engagement element has at least one protrusion which engages atleast one groove on the stud 74 to lock the stud 74 in place. FIG. 12Aillustrates an embodiment of a stud 74 of the present invention havingexternal grooves along its surface, in this instance external threads500. Here, the stud 74 is shown attached at one end to base 69 andhaving a threaded free end 502 which is coupleable with shaft 12 of thetool 10. It may be appreciated that the external grooves or threads 500may extend along any distance of the surface of the stud 74 and may haveany depth or spacing. Also it may be appreciated that the externalgrooves may comprise a series of cuts, indentations or threading whichmay or may not extend around the circumference of the stud 74. FIG. 12Billustrates an embodiment of the at least one engagement element havinggrooves, in this instance a split nut 506. The split nut 506 has acurved threaded surface 508 sized to mate with the external threads 500of the stud 74. Each split nut 506 also has at least one hinge component510 which is used to rotate or translate each split nut 506 within thelocking mechanism 106 to engage or disengage the external threads 500 ofthe stud 74.

FIG. 12C illustrates a pair of split nuts 506 disposed on opposite sidesof the stud 74, each split nut 506 having its curved threaded surface508 facing the external threads 500 of the stud 74. The split nuts 506are rotated or translated so that the threaded surfaces 508 are notengaging the external threads 500. In this position, the stud 74 is freeto move. Thus, when the split nuts 506 are rotated or translated outwardthe locking mechanism 106 is in an unlocked position wherein the stud 74is free to move the actuation mechanism 58 and therefore the distalelements 18 to any desired position. Rotation or translation of thesplit nuts 506 inward engages the curved threaded surfaces 508 with theexternal threads 500. Such engagement prevents motion of the stud 74,locking the distal elements 18 in place. It may be appreciated that anynumber of components may be present and each component may have anysuitable form to function as described above.

Many of the locking mechanisms of the present invention may be adaptedfor locking the fixation device 14 in a single predetermined position.Thus, rather than closing the distal elements 18 and locking the distalelements 18 in place at one of a multitude of optional locations, thedistal elements 18 may be closed and locked at a single predeterminedposition, such as at a 15, 30, 45 or 60 degree angle. For example, asmentioned above, the stud 74 may include a single groove 82 orindentation which receives the barbells 110. This may provide more rapidlocking by causing the barbells 110 to settle in a single position, aswell as indicating to the user that the fixation device 14 is locked ina known configuration. Likewise, FIG. 12D illustrates a lockingembodiment similar to the embodiment of FIG. 12C. Here, a split ring507, rather than a split nut, is disposed on opposite sides of the stud74. The split ring 507 has a curved projection 509 sized to mate with agroove 501 on the stud 74. Each split ring 507 also has at least onehinge component 510 which is used to rotate or translate each split ring507 within the locking mechanism 106 to engage or disengage the groove501 of the stud 74. For example, the split rings 507 may be rotated ortranslated so that the projections 509 are not engaging the groove 501.In this position, the stud 74 is free to move. Thus, when the splitrings 507 are rotated or translated outward the locking mechanism 106 isin an unlocked position wherein the stud 74 is free to move theactuation mechanism 58 and therefore the distal elements 18. Rotation ortranslation of the split rings 507 inward engages the curved projections507 with the groove 501. Such engagement prevents motion of the stud 74,locking the distal elements 18 in the predetermined position. It may beappreciated that any number of components may be present and eachcomponent may have any suitable form to function as described above.

In some embodiments, the locking mechanism comprises gears. Such gearsare used to incrementally translate the stud 74 in a forward or reversedirection which opens and closes the distal elements 18. Sincetranslation of the stud 74 is controlled by the gears, the stud 74 islocked in place when the gears are not moving. Thus, no additionallocking mechanism may be desired. FIGS. 13A-13C illustrate an embodimentof a fixation device 14 of the present invention having gears. Here, thestud 74 extends through the locking mechanism 106 as in previousembodiments. Advancement and retraction of the stud 74 moves the distalelements 18 (not show, for clarity) which are attached to the base 69.In this embodiment, the locking mechanism 106 comprises bevel gears.Referring to FIG. 13B, the bevel gears include a driving component 600and a driven component 602. The driving component 600 has a pedestal 604connectable with the housing 3 and a meshing surface 606 having gearteeth 607. The meshing surface 606 of the driving component 600 mesheswith gear teeth 609 of a meshing surface 608 of the driven component 602at an approximate angle of 90 degrees, or other suitable angle. Thedriven component 602 has a threaded interior 610 which mates withexternal threads 500 on the stud 74. Thus, rotation of the drivencomponent 602 causes advancement or retraction of the stud 74. Thedriving component 600 may be rotated by any suitable mechanism,including a gear belt or gear line 612. In this embodiment, two gearlines 612, 612′ are attached to the base 604 of the driving component600. Each gear line 612, 612′ is wound in the opposite direction so thatpulling one gear line 612 rotates the driving component 600 in aclockwise direction and pulling the other gear line 612′ rotates thedriving component 600 in a counterclockwise direction. Alternatively,one gear line may be employed and operated in a clockwise orcounterclockwise direction. The gear lines 612, 612′ extend from thelocking mechanism 106 through the coupling mechanism 19, as shown inFIG. 13A, and through the delivery catheter so as to be manipulable bythe user outside of the body. In other embodiments, illustrated in FIG.13C, two driving components 600, 600′ may be present, each drivingcomponent 600, 600′ meshed with the driven component 602. One gear line612 is connected with one driving component 600 and the other gear line612′ is connected with the other driving component 600′. Pulling thegear line 612 rotates driving component 600 which rotates the drivencomponent 602 causing advancement of the stud 74. Pulling the other gearline 612′ rotates the other driving component 600′ which rotates thedriven component 602 in the opposite direction causing retraction of thestud 74. It may be appreciated that a variety of gear mechanisms may beused including spur gears, helical and herringbone gears, miter gears,worms and worm gears, hypoid gears and rack and pinions, to name a few.

In some embodiments, the locking mechanism works against biasing forces,either inherent in the fixation device or created by the grasped tissue.As mentioned, the fixation device 14 includes a stud 74 for moving thedistal elements between open, closed, and inverted positions. In a “pullto close/push to open” embodiment, the distal elements 18 are pivotablycoupled to the stud 74 by a pair of legs or link members, wherebypushing the stud 74 pivots the distal elements 18 inwardly toward theclosed position. Once tissue has been grasped in a desired configuration(such as leaflets in a desired coapted arrangement), it may be desiredto hold the stud 74 in place by a locking mechanism. In this embodiment,the grasped tissue biases the fixation toward the open position since itrequires force to hold the tissues in place. Thus, the stud 74 is biasedtoward advancing (“pushing” to open). FIG. 14A illustrates the stud 74extending through housing 3 and holding the distal elements in a desiredposition wherein the fixation device 14 is biased towards opening, i.e.the stud 74 is biased towards advancing. To lock or hold the stud 74 inplace, an interference element, such as a locking sheath 640, isadvanced over the stud 74, as illustrated in FIG. 14B. The lockingsheath 640 fits snuggly over the stud 74 to prevent movement of the stud74 relative to the sheath 640 by, for example, friction or byinterlocking an internal threaded surface with threads 500 on the stud74. The sheath 640 is advanced so that its distal end 642 abuts thehousing 3 which is a stationary surface of the fixation device, asshown. Since the stud 74 is biased towards advancing, the distal end 642of the sheath 640 is held against the housing 3 preventing advancementof the stud 74 and hence locking the stud 74 in place. Upon decouplingof the fixation device 14 for implantation, as illustrated in FIG. 14C,the distal end 642 of the sheath 640 may also be decoupled from itsproximal end 644 for leaving behind with the fixation device 14. Thedistal end 642 may be removably joined with the proximal end 644 by anysuitable mechanism. In one embodiment, illustrated in FIG. 14D, theproximal and distal ends 642, 644 each have projections 646 which arepress-fit together in an alternating fashion. Thus, the proximal anddistal ends 642, 644 may be decoupled by pulling the ends 642, 644apart, disengaging the projections 646.

In a similar embodiment, illustrated in FIGS. 15A-15B, the interferenceelement comprises a lock nut 650 which holds the stud 74 in place. FIG.15A illustrates the stud 74 extending through housing 3 and holding thedistal elements (not shown for clarity) in a desired position whereinthe fixation device 14 is biased towards opening, i.e. the stud 74 isbiased towards advancing. A lock nut 650 is screwed down over threads500 by means of a torqueable sleeve 652 which is advanced over the stud74. The torqueable sleeve 652 is joined with the lock nut 650 by anysuitable means to provide torqueable attachment, such as projectionsinto the lock nut 650, etc. The sleeve 652 is advanced until the locknut 650 abuts the housing 3, as shown in FIG. 15B. Since the stud 74 isbiased towards advancing, the lock nut 650 is held against the housing 3preventing advancement of the stud 74 and hence locking the stud 74 inplace. The sleeve 652 may then be removed and the fixation device 14decoupled for implantation. It may be appreciated that the distal end642 of the locking sheath 640 of FIGS. 14A-14D may also be considered alock nut utilized in the same fashion. It may also be appreciated thatthe lock nut 650 may have external threads which mate with threads onhousing 3. By screwing the lock nut 650 into the housing, the stud 74may be prevent from advancing or retracting. Thus, such a lockingfeature may be used with fixation devices 14 which are not biased towardopening or closing.

In another embodiment, illustrated in FIGS. 16A-16B, the stud comprisesa suture line 75 or other flexible line. FIG. 16A illustrates the line75 extending through housing 3 and allowing the distal elements (notshown for clarity) to move to a desired position wherein the fixationdevice 14 is biased towards opening, i.e. the line 75 is biased towardsadvancing. A suture fastener 698 is advanced down the line 75 until thefastener 698 abuts the housing 3 as shown in FIG. 16B. Since the line 75is biased towards advancing, the fastener 698 is held against thehousing 3 preventing advancement of the line 75 and hence locking thedistal elements in place. The line 75 may then be cut proximal to thefastener 698 and the fixation device 14 decoupled for implantation.

As mentioned above, in many embodiments the distal elements 18 arepivotably coupled to the stud 74 by legs 68, whereby retracting the stud74 pivots the distal elements 18 inwardly toward the closed position. Insome embodiments, as illustrated in FIG. 17A, the legs 68 are springbiased toward the closed position. This may be achieved by forming thelegs 68 from a continuous flexible material, such as cobalt chromium,stainless steel, Nitinol, Elgiloy® and the like. Opening of the distalelements 18 flexes the legs 68 outward, storing potential energytherein. Once the fixation device 14 has been desirably positioned,grasping tissue therebetween, the distal elements 18 are released andthe legs 68 recoil toward the closed position, holding the distalelements 18 against the grasped tissue, thereby locking the distalelements 18 in place.

In other embodiments, the distal elements 18 are biased toward theclosed position by the application of a biasing member. For example, asshown in FIGS. 17B-17C, the biasing member 670 may be comprised of apair of support sleeves 672 mounted on a rod 674. The rod 674 may beadvanced through the stud 74 so that the sleeves 672 are disposeddistally of the fixation device 14. This allows the fixation device 14to open, close, and/or invert as desired. Once the distal elements 18have satisfactorily grasped the tissue, the distal elements 18 may belocked in place by retracing the rod 674 which slides the supportsleeves 672 over the legs 68, as illustrated in FIG. 17C. The supportsleeves 672 are comprised of a flexible material, such as cobaltchromium, stainless steel, Nitinol, Elgiloy® and the like, so thatopening of the support sleeves 672 flexes the support sleeves 672outward, spring loading the sleeves 672 and storing potential energytherein. The stored spring force then biases the sleeves 672 toward theclosed position, holding the distal elements 18 against the graspedtissue, thereby locking the distal elements 18 in place.

In other embodiments, the biasing member 670 comprises a cinching band.The cinching band may be elastic or substantially inelastic. Anembodiment of an elastic cinching band 680 is illustrated in FIGS.18A-18C. During positioning of the fixation device 14, the elasticcinching band 680 may be disposed distally of the distal elements 18,such as around the legs 68, as illustrated in FIG. 18A. This allows thedistal elements 18 to be moved between open, closed and/or invertedpositions as desired while grasping the tissue in a desiredconfiguration. Once the tissue has been satisfactorily grasped, thedistal elements 18 may be locked in place by repositioning of the band680. The band 680 may be repositioned with the use of an adjustment line682, such as a suture or wire, which is joined with the band 680. Asillustrated in FIG. 18B, the band 680 may be pulled in the proximaldirection by retracting the adjustment line 682. This draws the band 680over the distal elements 18 in a stretched configuration, as illustratedin FIG. 18C. Stretching of the elastic cinching band 680 storespotential energy therein. The stored spring force then biases the distalelements 18 toward the closed position, holding the distal elements 18against the grasped tissue, thereby locking the distal elements 18 inplace. The distal elements 18 may also include grooves 684 into whichthe band 680 may be placed. Such grooves 684 may reduce possibleslippage of the band 680 and indicate to the user a desired positionalong the distal elements 18 for placement. The adjustment line 682 isthen removed and the fixation device 14 left in place. It may beappreciated that an inelastic cinching band would function similarly.One difference is that the inelastic band may hang loosely around thelegs 68 and would be taut when positioned around the distal elements 18.The distal elements 18 are locked at a position based on the length ofthe inelastic cinching band whereas the distal elements 18 would be helda position based on the stored potential energy of the elastic cinchingband.

In other embodiments, the cinching band comprises a cinching line 690,as illustrated in FIGS. 19A-19C. The cinching line 690 is typicallycomprised of a substantially inelastic material, such as a suture,thread or filament. The cinching line 690 is wrapped around the fixationdevice 14 in a “lasso”-type configuration. Typically, the cinching line690 has a loop 692 at one end through which the line 690 passes so thatpulling on the line 690 tightens the lasso. In one embodiment,illustrated in FIG. 19A, the cinching line 690 is wrapped loosely aroundthe distal elements 18. This allows the distal elements 18 to be movedbetween open, closed and/or inverted positions as desired while graspingthe tissue in a desired configuration. The line 690 may be adhered tothe distal elements 18 (or other parts of the fixation device) atvarious locations 694 to assist in keeping the line 690 in place. Oncethe tissue has been satisfactorily grasped, the distal elements 18 maybe locked in place by tightening the cinching line 690. The cinchingline 690 may be tightened by pulling the line 690 in the proximaldirection so the lasso tightens around the distal elements 18, asillustrated in FIG. 19B. Such tightening allows the line 690 to breakfrom the adhered locations 694. The cinching line 690 biases the distalelements 18 toward the closed position, holding the distal elements 18against the grasped tissue, thereby locking the distal elements 18 inplace. The distal elements 18 may be held at any desired position byapplying more or less force to the cinching line 690. It may beappreciated that the distal elements 18 may also include grooves intowhich the line 690 may be placed. Such grooves may reduce possibleslippage of the line 690 and indicate to the user a desired positionalong the distal elements 18 for placement. Referring to FIG. 19C, asuture fastener 698 is then advanced along the cinching line 690 andpositioned against the loop 692 to hold the line 690 in place. The line690 is then cut proximal to the suture fastener 698 and the fixationdevice 14 left in place.

In some embodiments, the locking mechanism is comprised of structures,such as barbs, which attach to the legs, holding the legs in a fixedposition. FIG. 20 illustrates an embodiment of such a locking mechanism.Here, barbs 700 extend outwardly from the housing 3 toward the legs 68.The barbs 700 are segmented so that the barbs 700 can be extendedthrough the legs 68 to variable extents which in turn allows the distalelements 18 to be locked at various positions. FIGS. 21A-21C illustratesuch attachment to the legs 68. FIG. 21A illustrates a barb 700approaching a leg 68. The leg 68 has a hole 702 which is covered by aflap 703. As the distal element 18 rotates toward the closed position,the leg 68 is drawn toward the barb 700. Referring to FIG. 21B, the barb700 then advances through the hole 702, pushing the flap 703 open. FIG.21C illustrates a first segment 706 of the barb 700 extending throughthe hole 702 wherein the flap 703 recoils and wedges against the barb700. This holds the barb 700 in attachment with the leg 68. The leg 68is now locked in place, thereby locking the associated distal element 18in place. Additional segments of the barb 700 may be advanced throughthe leg 68 to lock the distal elements 18 in more closed positions. Itmay also be appreciated that the barb 700 may only include a firstsegment 706 wherein the leg 68 may be locked in a single position,rather than allowing variable positions.

It is further within the scope of the present invention that the lockingmechanism be a wedge contacting a sloped surface, a threaded engagement,a spring, a groove engaging protrusion, a ratchet mechanism, a pinengaging a hole, a magnet attracting to a dipole magnet, a gearedmechanism pulley or belt mechanism and the like. Further, the lockmechanism may include use of epoxy resin, energy (such as radiofrequencyor ultrasonic welding) to bind the stud relative to the housing.

It may be appreciated that the locking mechanisms of the presentinvention may be utilized in a variety of fixation devices having anynumber and combination of proximal and/or distal elements. For example,the locking mechanisms may be used in combination with a device having asingle distal element or a single pair comprising one proximal elementand one distal element wherein a leaflet or other tissue is graspedbetween the proximal and distal element of the pair. In another example,the locking mechanisms may be used in combination with a device havingmultiple distal elements, such as three distal elements. In general, thelocking mechanisms of the present invention may be used to lock anymoveable elements in place.

It may further be appreciated that the locking mechanism of the presentinvention may also be utilized in other devices and systems, such as tolock catheters, retractors, or other medical instruments such asgraspers or biopsy forceps in a particular position prior to, during, orfollowing a medical procedure. Examples of catheters include steerableguide catheters, such as described in U.S. patent Ser. No. 10/441,753incorporated herein by reference, and inner and/or outer guidecatheters, such as described in U.S. patent Ser. No. 10/441,531incorporated herein by reference. In these examples, the lockingmechanism of the present invention function as the locking actuators.

FIG. 22 illustrates a proximal end of a catheter 1600 having anembodiment of a locking mechanism 106 of the present invention. Here,the stud 74 is fixedly attached to a pullwire 1602 which extends alongthe catheter 1600, typically within a lumen 1604 in the wall of thecatheter 1600. In this embodiment, a knob 1606 is connected with thestud 74 and extends radially outwardly through an opening 1608 in thecatheter 1600. The opening 1608 is shaped to allow axial movement of theknob 1606 along the length of a portion of the proximal end of thecatheter 1600. Axial movement of the knob 1606 in turn moves the stud 74and attached pullwire 1602 which in turn steers the catheter 1600. Thepullwire 1602 can be locked in any desired axial position by the lockingmechanism 106. The locking mechanism includes one or more wedgingelements 1610 which wedge against the stud 74 to hold the stud 74 andattached pullwire 1602 in a desired axial position. FIG. 22 illustratesthe locking mechanism of FIGS. 4A-4C, however it may be appreciated thatany of the locking mechanism disclosed herein may be used. When in theunlocked position, the stud 74 is free to move. When in the lockedposition, a spring forces the wedging elements 1610 downwards and wedgesthe wedging elements 1610 between a sloping surface and the stud 74.This restricts motion of the stud 74, which in turn locks the pullwire1602 in place.

FIG. 23 illustrates an endoscopic grasper 1620 having an embodiment of alocking mechanism 106 of the present invention. The grasper 1620comprises an elongate shaft 1622 rotateably coupled at its distal endwith a pair of jaws 1624. The jaws 1624 are spring loaded so that thejaws 1624 are in a closed position unless tension is applied to a pairof pullwires 1626 which draw the jaws 1624 toward an open position. Theshaft 1622 and pullwires 1626 extend through a tubular sheath 1628 asshown. The jaws 1624 may be locked in any position including the closedposition, a fully open position and any position therebetween. This maybe achieved with a locking mechanism 106 of the present invention. Here,the stud 74 is fixedly attached to the pullwires 1626 which extend alongthe shaft 1622 to the proximal end of the sheath 1628. In thisembodiment, a knob 1606 is connected with the stud 74 and extendsradially outwardly through an opening 1608 in the sheath 1628. Theopening 1608 is shaped to allow axial movement of the knob 1606 alongthe length of a portion of the proximal end of the sheath 1628. Axialmovement of the knob 1606 in turn moves the stud 74 and attachedpullwires 1626 which in turn steers the catheter 1600. The pullwire 1602can be locked in any desired axial position by the locking mechanism106. The locking mechanism includes one or more wedging elements 1610which wedge against the stud 74 to hold the stud 74 and attachedpullwires 1626 in a desired axial position.

FIG. 23 also illustrates an additional grasper 1650 advanceable througha lumen in the shaft 1622 of the endoscopic grasper 1620. Here, theadditional grasper 1650 has an elongate shaft 1652 coupled with a stud74 of a locking mechanism 1610. Advancement and retraction of the stud74 opens and closes a pair of jaws 1654 so that the jaws 1654 aremoveable in a manner similar to the distal elements of the abovedescribed fixation devices. Thus, the jaws 1654 may be locked in placeby the locking mechanism 1610 as described above. It may be appreciatedthat the jaws 1624 of the endoscopic grasper 1620 may be locked in thismanner as an alternative to the locking mechanism disposed near itsdistal end.

FIG. 23 illustrates the locking mechanism of FIGS. 4A-4C, however it maybe appreciated that any of the locking mechanism disclosed herein may beused. When in the unlocked position, the stud 74 is free to move. Whenin the locked position, a spring forces the wedging elements 1610downwards and wedges the wedging elements 1610 between a sloping surfaceand the stud 74. This restricts motion of the stud 74, which in turnlocks the pullwire 1602 in place.

It may be appreciated that locking mechanisms of the present inventionmay be disposed within or near a distal portion of a device where spaceis limited, along an elongate portion of the device (particularly ifmultiple locking mechanisms are desired), or within or near a proximalend of the device (such as illustrated in FIGS. 22-23). Multiple lockingmechanisms may be desired when multiple pullwires are used to steer asheath or catheter. Thus, the multiple locking mechanisms can assist inpositioning instruments in tortuous body paths or locations.

Although the foregoing invention has been described in some detail byway of illustration and example, for purposes of clarity ofunderstanding, it will be obvious that various alternatives,modifications and equivalents may be used and the above descriptionshould not be taken as limiting in scope of the invention which isdefined by the appended claims.

1. An implantable fixation device for engaging cardiac tissuecomprising: a pair of elements each having a first end, a free endopposite the first end, and an engagement surface therebetween forengaging the tissue, the first ends being moveable between an openposition wherein the free ends are spaced apart and a closed positionwherein the free ends are closer together with the engagement surfacesgenerally facing each other, wherein the pair of elements in the closedposition are adapted to reduce retrograde blood flow across the engagedtissue; a locking mechanism coupled to the elements for locking theelements in place along a continuum of positions between the openposition and the closed position; a moveable stud pivotably coupled toboth the elements wherein movement of the stud moves both the elementsbetween the positions, the locking mechanism comprising at least onewedging element for frictionally engaging the stud to restrict movementthereof, the at least one wedging element comprising a binding platehaving a first end, a second end and a portion therebetween shaped toengage the stud, the binding plate positioned so that the portion isdisposed near the stud; and an unlocking mechanism for disengaging thelocking mechanism, wherein the unlocking mechanism comprises a harness,the harness adapted to move the second end while the first end remainssubstantially stationary so as to reduce frictional engagement of the atleast partially surrounding portion with the stud.
 2. A fixation deviceas in claim 1, further comprising an unlocking mechanism for disengagingthe locking mechanism so the elements are moveable.
 3. A fixation deviceas in claim 1, wherein the portion shaped to engage the stud at leastpartially surrounds the stud, the binding plate positioned so that theportion at least partially surrounds the stud.
 4. A fixation device asin claim 3, wherein the portion shaped to at least partially surroundthe stud comprises an aperture, the binding plate positioned so that thestud passes through the aperture.
 5. A fixation device as in claim 4,wherein the locking mechanism further comprises a spring which forcesthe aperture against the stud to restrict movement of the stud throughthe aperture.
 6. A fixation device as in claim 1, wherein the at leastone wedging element comprises at least one cam, the at least one campivotable to frictionally engage the stud to restrict movement thereof.7. A fixation device as in claim 6, wherein the at least one cam has aninward surface engageable with the stud and an outward surface connectedwith a spring which forces the inward surface against the stud torestrict movement of the stud.
 8. A fixation device as in claim 7,further comprising an unlocking mechanism for disengaging the lockingmechanism, wherein the unlocking mechanism comprises at least oneactuator attached to a pivot point on each of the at least one cams, theat least one actuator adapted to pivot the at least one cam about itspivot point to reduce frictional engagement of the inner surface withthe stud.
 9. A fixation device as in claim 6, wherein the at least onecam comprises two cams, each cam disposed on opposite sides of the stud.10. A fixation device as in claim 2, wherein the unlocking mechanismcomprises a lock line operably coupled with the harness such that anupwards force in the lock line actuates the harness so as to move thesecond end.